Denise Camp was resigned to the double standard that had long applied to her medical bills, forcing her to skimp on other expenses so she could pay for mental health treatment.

While visits to her internist for physical problems required a $20 co-pay, her weekly therapy sessions with a social worker cost $50 and trips to the psychiatrist who prescribed her medication were $75. A similar disparity applied to medicines: Drugs to treat the crippling depression that ended her engineering career cost her twice what she paid for an antibiotic.

But recently, Camp's insurance coverage changed -- for the better. The 50-year-old Baltimore resident, who now runs a drop-in center for recovering psychiatric patients, is paying the same charge for physical and mental health treatments: a co-pay of $10 per visit and $25 for each prescription.

"I have to use mental health benefits no matter what," said Camp, who is insured through her employer. "This is going to make it more affordable for me."

Camp is among an estimated 140 million Americans, most of them covered by group insurance plans provided by employers, who are the beneficiaries of a sweeping new federal law designed to guarantee parity in insurance coverage.

The law, which took effect for most plans Jan. 1, applies to groups of more than 50 employees and is designed to end what Health and Human Services Secretary Kathleen Sebelius called "needless and arbitrary limits on care." Higher deductibles, steeper co-pays and other restrictions are no longer allowed for mental health and substance abuse treatment.

The law does not apply to individual insurance policies, nor does it require group plans to provide mental health and substance abuse treatment, although most do.

Several weeks ago the Obama administration issued 154 pages of regulations governing implementation of the law, which was sponsored by the late Sen. Paul Wellstone (D-Minn.) and former Sen. Pete V. Domenici (R-N.M.). Passed with broad bipartisan support and signed into law by President George W. Bush in 2008, the measure is widely regarded as the last major piece of health legislation passed by Congress. The rules, which are subject to a comment period, are scheduled to take effect July 1.

Officials of key business and insurance industry groups said they were displeased that the regulations were "more expansive" than they believe lawmakers intended. Mental health advocates applauded the rules, which they said would help ensure that Americans battling schizophrenia, for example, receive the same level of care provided to those facing leukemia.

"This is a great boon for people like me who use these benefits," said Peter Schroeder, 36, a computer scientist in Berkeley, Calif., who has received treatment for depression and alcohol abuse.

"These are serious conditions that get really expensive really quickly," said Kirsten Beronio, a vice president of Mental Health America, an advocacy group based in Alexandria.

Some families, she noted, have gone bankrupt trying to pay for treatment. In extreme cases, parents of troubled children who need expensive, intensive services have been forced to temporarily relinquish custody to the state so that their children could qualify for services paid by Medicaid.